A medical device represented by a swallow type capsule endoscope or the like which is administered into an object under test such as a subject or the like and passed through a coelomoduct to obtain images in the coelomoduct at a target position has been recently studied and developed for the purpose of its practical use. The medical device such as the capsule endoscope or the like is equipped with an image pickup element such as CCD (Charge Coupled Device) or the like which can perform the above medical action, for example, obtain an image, and obtain an image at a target site in the coelomoduct.
It is necessary that the capsule endoscope is controlled to be guided irrespective of peristalsis of the coelomoduct so that the capsule endoscope is made to surely reach a target site in the coelomoduct or stay at a target site to be subjected to detailed examination or the like which needs time. In order to guide the capsule endoscope, it is required to detect a place at which the capsule endoscope is located in the coelomoduct, and there has been proposed a technique of detecting the position of the capsule endoscope guided to a place (the inside of a coelomoduct or the like) which cannot be visually checked (for example, see Patent Citation 1). Furthermore, a method of detecting the position and direction of a wireless magnetic marker is disclosed in Patent Citation 2.
The Patent Citation 1 discloses a technique that electromagnetism occurring from a capsule endoscope having a magnetic field generating field in which an LC resonance circuit is connected to an alternate power source is detected by plural external detection devices to detect the position of the capsule endoscope.
Furthermore, the Patent Citation 2 discloses a resonance circuit containing a magnetic induction coil having a magnetic core as a wireless magnetic marker. According to the method of the Patent Citation 2, the position and direction of the wireless magnetic maker can be detected by utilizing the fact that a given external magnetic field is varied due to existence of a resonance circuit having a magnetic induction coil containing a wireless magnetic marker therein.    Patent Citation 1: PCT International Publication No. WO2004/014225 A1 Pamphlet    Patent Citation 2: Japanese Unexamined Patent Application, Publication No. 2005-121573